The present invention relates to a pulley useable in a belt-driven continuously variable transmission (CVT), for example, a belt-driven CVT as a power transmission of vehicles, and to a process for making a moveable pulley half of the pulley.
There is a known belt-driven CVT as shown in FIG. 5. The belt-driven CVT includes an input pulley 102 mounted to an input shaft 101 drivingly connected with a power source, an output pulley 103 mounted to an output shaft (not shown), and an endless driving belt 104 connecting the input and output pulleys 102 and 103. The input pulley 102 includes a fixed pulley half 105 integrally formed with the input shaft 101 and a moveable pulley half 106 reciprocally moveable in an axial direction of the input shaft 101. The fixed and moveable pulley halves 105 and 106 include tapered contact surfaces 105a and 106a that are axially opposed to each other and frictionally contacted with the driving belt 104. Similarly, the output pulley 103 includes fixed and moveable pulley halves 107 and 108 having tapered contact surfaces 107a and 108a, respectively. The driving belt 104 displaces in a radial direction of each pulley 102 and 103 as the moveable pulley half 106 and 108 of the pulley 102 and 103 reciprocally moves. The revolution of the input rotating shaft 101 is continuously variably transmitted to the output rotating shaft through the input and output pulleys 102 and 103 and the driving belt 104 depending on continuous radial displacement of the driving belt 104. The moveable pulley half 106 of the input pulley 102 includes a shaft portion 109 mounted to the input shaft 101, a radially outwardly extending flange portion connected with the shaft portion 109, a step portion 111 formed in the flange portion, and an annular cylinder member 110 press-fitted to the step portion 111. The cylinder member 110 fixed to the moveable pulley half 106 is slidably received within a partition wall 115 and cooperates therewith to define a pressure chamber therebetween. Working fluid is fed to the pressure chamber through a communication hole 112 formed in the shaft portion 109. The output pulley 103 has substantially the same structure as that of the input pulley 102.
The moveable pulley half 106 with the cylinder member 110 is formed by the process shown in FIGS. 6A-6F. In FIGS. 6A-6F, only an upper half of a cross-section of the moveable pulley half 106 taken along an axis thereof is shown for the purpose of simple illustration. FIGS. 6E and 6F also show only an upper half of a cross-section of the cylinder member 110.
As illustrated in FIG. 6A, a workpiece 150 having a predetermined shape is formed by forging. Then, as illustrated in FIG. 6B, the workpiece 150 is machined to form the shaft portion 109, the flange portion, the step portion 111 and the communication hole 112. The workpiece 150 machined is heat-treated as indicated by the broken line in FIG. 6C. As illustrated in FIG. 6D, the workpiece 150 heat-treated is then finished to form the moveable pulley half 106 having the contact surface 106a. On the other hand, the cylinder member 110 is formed from sheet metal by a suitable method such as pressing, as shown in FIG. 6E. Finally, as illustrated in FIG. 6F, the cylinder member 110 is press-fitted to the step portion 111 of the moveable pulley half 106. Incidentally, the communication hole 112 is formed before the press-fitting of the cylinder member 110 because the cylinder member 110 is located on a hypothetical extension line extending in a longitudinal direction of the communication hole 112.